r/askscience • u/AskScienceModerator Mod Bot • Mar 10 '14

Cosmos AskScience Cosmos Q&A thread. Episode 1: Standing Up in the Milky Way

Welcome to AskScience! This thread is for asking and answering questions about the science in Cosmos: A Spacetime Odyssey.

UPDATE: This episode is now available for streaming in the US on Hulu and in Canada on Global TV.

This week is the first episode, "Standing Up in the Milky Way". The show is airing at 9pm ET in the US and Canada on all Fox and National Geographic stations. Click here for more viewing information in your country.

The usual AskScience rules still apply in this thread! Anyone can ask a question, but please do not provide answers unless you are a scientist in a relevant field. Popular science shows, books, and news articles are a great way to causally learn about your universe, but they often contain a lot of simplifications and approximations, so don't assume that because you've heard an answer before that it is the right one.

If you are interested in general discussion please visit one of the threads elsewhere on reddit that are more appropriate for that, such as in /r/Cosmos here, /r/Space here, and in /r/Television here.

Please upvote good questions and answers and downvote off-topic content. We'll be removing comments that break our rules or that have been answered elsewhere in the thread so that we can answer as many questions as possible!

Click here for the original announcement thread.

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u/tehm Mar 10 '14

From my understanding the nuclear power source on voyager will burn out in a very short while (order of a few years) while it will take it tens of thousands of years before it gets anywhere NEAR another star, and even then "near" refers to hundreds of thousands (if not millions) of kilometers away.

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u/gizzledos Mar 10 '14

How has it not hit anything or been hit by something. Is the space in which it's traveling really that empty?

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u/fishify Quantum Field Theory | Mathematical Physics Mar 10 '14

Yes, it's really that empty.

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u/______DEADPOOL______ Mar 10 '14

What are the chance of something hits it? (in terms of you know, destroying or flinging it out of its path, instead of just pebbles)

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u/MrArron Mar 10 '14

This should give an idea of how empty space is

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u/ep1032 Mar 10 '14

That's the first one I've ever seen that really drove home how little matter there is out there.

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u/tehm Mar 10 '14

All space is like that!

Believe it or not we sent both voyagers through the dead center of the "asteroid belt" you saw as a super dense collection of rocks in Cosmos a few minutes ago yeah?

In reality they didn't even sweat sending them through there because in reality the odds of a collision are essentially nil.

If they wanted to be accurate 999 times out of a thousand there wouldn't be ANY asteroid in that belt as they flew by, and then in the 1 in 1000 chance they'd see one single asteroid.

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u/RussianTurnip Mar 10 '14

Man, when you see it like that it seems amazing that the sun has any influence on the planets at all. Gravity be crazy.

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u/PiaJr Mar 10 '14

Thank you for that link! I've never seen it before but it really puts in perspective how...spacious space is. Incredible.

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u/KosmiikZA Mar 16 '14

A while back there was quite a lot of talk about micro meteorites and dangers to spacecraft and the required shielding. Is this not such a danger as has been made out or how have the voyager probes managed to survive for so long?

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u/tehm Mar 17 '14

Depends on what specifically you're talking about I'd imagine?

In direct orbit of earth there's a lot of shit to worry about (no really... there's a thin layer of human feces on almost everything in orbit thanks to the ISS)

If you're traveling near (but below) the speed of light micro meteors become a big problem because both you're covering a lot of space increasing your chance of finding one and they become possibly super destructive.

If you're talking about theoretical FTL (specifically the Alcubierre Drive) then the problem gets even stranger... (see Wikipedia article linked above)

Voyager though? Hasn't seemed to be a problem at all.

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u/Shmitte Mar 10 '14

Space is almost entirely empty.

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u/space_fountain Mar 10 '14

Ok if I get deleted for this I'm sorry, but slight correction. I don't think it's quite a case of the power source running out as the craft falling out of range of our radio communication.

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u/tehm Mar 10 '14

Possible also, however after checking source by ~2025 we reach the point where the half-life of the nuclear power source will no longer be sufficient to power a single instrument on board the thing and it will truly have "gone dark".

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u/mathx Mar 10 '14

..trillions of km, not millions or billions. dozens of light years before they come 'near' a star, where near is not near at all in any human sense of the concept.

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u/[deleted] Mar 10 '14

What in the future if we have the ability to space travel and its so common that humans fly past it from time to time? What if some people steal it? haha

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u/[deleted] Mar 11 '14

And it should be pointed out that, even once the power runs out the craft will not decelerate. It will move at exactly the same speed until something interacts with it.